Australian Monthly Climate Summary: July 2009

Monday 3 August 2009

In Brief

July 2009 was generally warmer than normal, with average to below average rainfall totals covering much of the continent. Some southern parts, mainly near the coast, had a wetter than normal month. When averaged across the country, rainfall was well below the long-term mean. The exceptions to the warmer than average conditions were southwest WA, where daytime temperatures were generally cooler than normal, and central to northern Queensland, where overnight temperatures were suppressed.

Details

Temperatures:

For the month of July 2009, daytime maximum temperatures were generally warmer than the long-term average across most of the continent. Southwest WA was the only part of Australia to see daytime maximum temperatures slightly cooler than the long-term mean. Maximum temperatures were generally 1 to 2°C above average over most of northern Australia as well as in coastal districts of eastern Victoria. Queensland and Tasmania had their ninth warmest July days on record (Tasmania was tied equal ninth) and Victoria its seventh.

Overnight minimum temperatures were also above average over much of the continent. The exception was an area covering central to northern Queensland and the north of the NT, where cooler than normal nights were recorded. Overnight minima were generally 1 to 3°C below average in some areas near the Gulf of Carpentaria, especially in Queensland. In contrast, nights were 1 to 3°C warmer than average across a broad zone stretching from northwest WA to southeastern Australia. Most of SA and the Eucla district in WA saw overnight temperatures in the highest 10% (decile 10) of 60 years of records, with many observations sites along the SA west coast and the Eyre Peninsula recording their highest July mean minimum on record. State averages were the fourth highest in SA, ninth highest in Victoria and tenth highest in Tasmania.

While much of the continent recorded below average rainfall during July 2009, a substantial area of southern WA, southern SA, southwestern Victoria and western Tasmania recorded wetter than normal conditions. Several observation sites scattered across these regions recorded rainfall in the highest 10% (decile 10) of 110 years of records. When averaged across the state, Tasmania recorded its highest July rainfall since 2002, while the SA agricultural area recorded its highest July rainfall since 1996.

For the rest of Australia, July rainfall was generally below average. As mentioned in the introduction, when average across the continent, rainfall was well below the long-term mean (37% below normal). A large area of central and southern Queensland recorded rainfall in the lowest 10% (decile 1) of 110 years of records, with a few sites in eastern Queensland recording their lowest July rainfall on record. The Queensland state-wide average was the fifth lowest on record for July. However, it is important to note that rainfall is commonly low over most of Queensland at this time of the year. The NSW state average 45% below normal, while rainfall over the Murray-Darling Basin was 43% below normal.

Table 2: Spatial Rainfall Summary

Area

Rank*(out of 110)

Average (mm)

Departurefrom mean

Comment

Australia

20

13.9

−37%

Queensland

5

1.2

−93%

New South Wales

25

20.6

−45%

Victoria

53

64.6

−10%

Tasmania

86

185.4

+16%

South Australia

64

17.8

−6%

Western Australia

43

16.9

−18%

The Northern Territory

38

0.4

−94%

Murray-Darling Basin

21

22.2

−43%

*Fractional ranks denote tied values.

**A new area-averaging method has been adopted for rainfall from May 2009. Current and
historical totals for Tasmania are substantially higher than under the old scheme, but differences
for other states, and nationally, are negligible.